1. Field of the Invention
The invention relates to devices for sending and receiving messages between an electronic control unit and an external device, especially with electronic control units of a vehicle and an external device, such as an emissions tester.
2. Description of Related Art
Numerous government municipalities perform periodic testing of emissions outputted automobiles. These emissions testing devices may be standalone devices that only perform emissions testing or may be general purpose computers that are loaded with the appropriate software that performs emissions testing. An emission testing device is generally performed by connecting the emissions tester to a port that is in communication with electrical systems of the vehicle. The communications port is normally located between the dashboard and the brake pedal. It is most likely to be a Society of Automotive Engineers (“SAE”) J1962 port—better known as an On-Board Diagnostics II (“OBD-II”) port. This port allows communication from connected devices to any of the available busses on the vehicle. The bus is connected to numerous electronic control units located within the vehicle as well as sensor systems that are also located within the vehicle. These sensor systems routinely collect data relating to the operation of the automobile, including emissions related data. The emissions tester connected to the port will then communicate with these systems and electronic control units regarding emissions related information of the vehicle. The emissions testing device or related software will analyze this data and make a determination if the vehicle has met the municipality's standards for emissions relating operation. OBD-II port may be any one of K-Line, J1850PWM, J1850VPW or CAN and that these are on separate pins of the OBD-II port.
However, many automotive enthusiasts commonly perform modifications to their vehicle that may confuse the emissions testing device. This confusion of the emissions testing device can lead the emissions testing device to make a determination that the vehicle has not passed emissions and thereby causing the owner of the vehicle to spend resources to further modify their vehicle to correctly pass emissions. This can occur in situations where the vehicle is passing emissions but because of the confusion caused by the modifications to the emissions tester, the emissions tester reports that the automobile has failed the test.